1. Field of the Invention
The present invention relates to a linear roller bearing, in which rolling elements are interposed between a pair of raceway blocks (or so-called ways) formed with raceway grooves at longitudinal side-wall surfaces thereof to allow relative motion between the raceway blocks.
2. Description of the Prior Art
A conventional linear roller bearing, as shown in FIG. 8, consists of: a pair of ways 1, 2 parallelly facing each other and so set that they can move relative to each other; a cage 5 disposed between the way 1 and the way 2; and cylindrical rollers 7 supported in the cage 5 and interposed between a raceway groove 3 of the way 1 and a raceway groove 4 of the way 2. A longitudinally extending side-wall surface la of the way 1 is formed with a roughly V-shaped raceway groove 3 that has an upper raceway surface 3a, a lower raceway surface 3b and a cutter escape groove 3c. A longitudinally extending side-wall surface 2a of the way 2 is formed with a roughly V-shaped raceway groove 4 that has an upper raceway surface 4a, a lower raceway surface 4b and a cutter escape groove 4c. Longitudinal end surfaces of the ways 1, 2 are formed with threaded holes 9, and one of the ways 1, 2 is fitted with a stopper or end screw 10 to prevent a deviation of the cage 5. The ways 1, 2 have mounting surfaces 1b, 2b to be brought into contact with a base or table, and mounting holes 1c, 2c formed in the mounting surfaces 1b, 2b.
In this linear roller bearing, the cage 5 is normally made of a metal material and has roller retaining holes 6 formed therein at equal intervals. To support the cylindrical rollers 7 in the cage 5, claws 20 are cut and raised at the upper and lower edge portions of the roller retaining holes 6 in the cage 5 to hold the cylindrical rollers 7 in the roller retaining holes 6. The cylindrical rollers 7 are arranged in two directions so that adjacent ones cross each other.
This linear roller bearing has a simple structure, allows very high precision machining to be done to the raceway surfaces of the raceway grooves 3, 4, and incorporates in the cage 5 ultra-precise cylindrical rollers 7 whose diameter dimensions are strictly controlled. Because of these features, the linear roller bearing can provide a very smooth linear motion with very small friction resistance and therefore has found a wide range of applications with precision measuring devices and precision machining equipment.
The linear roller bearing mentioned above, however, has the possibility that the cage may slip or become dislocated when used under conditions where the stroke frequency of the ways is high and where the bearing is subjected to vibrations and unequally distributed load. For this reason, a stopper or end plate provided at the longitudinal ends of the ways against which the cylindrical rollers carried in the cage abut cannot be eliminated. Especially when the pair of ways move relative to each other, the cage also move relative to the ways. The relative motion of the cage with respect to the ways is not uniform, causing the cage to deviate or slip from the ways, so that it is difficult to maintain the cage in an appropriate position with respect to the ways.
Japanese Utility Model Laid-Open No. 89523/1987 discloses a sealing apparatus for a linear roller bearing. In this sealing apparatus for the linear roller bearing, the facing surfaces of two ways of square column are each formed with a longitudinally extending, roughly V-shaped raceway groove, with rolling elements carried in the cage trapped between the raceway grooves. The cage is a thin plate which has windows or roller retaining holes formed therein at equal intervals to hold the rolling members. At least the roller retaining holes at the ends of the cage are firmly fitted with a sealing member roughly the same in cross section as the rolling members.